Vibrations, stray voltage, noise ... and dairy cows
By Alejandro R. Castillo,
UCCE Merced County
It is expected that in this 21st century, both developed and developing countries will be consuming more energy from electricity for production and transportation. Electrical and hybrid technologies have been introduced to reduce or mitigate the emission of harmful air pollutants.
California dairy farms are required to comply with air quality regulations that mandate that all stationary and transportable internal combustion engines greater than 50 horsepower (bhp), including emergency back-up generators, shall be replaced with electric motors (San Joaquin Valley Air Pollution Control District, Rule 4702).
Because of the increasing use of electricity in transportation systems (trams, trains, and hybrid cars), the issue of electromagnetic fields has arisen. In the near future, dairy animals might be exposed to new and/or different environmental effects, like noises, vibrations, stray voltage, and electromagnetic fields. The goal of this article is to summarize technical information related to these effects on lactating dairy cows. (Peer reviewed papers and technical articles used may be requested from the author.)
Cows are exposed daily to a variety of high intensity noises such as pumps, electric motors, etc. A wide range of studies have been conducted concerning noise effects on animals, including jet aircraft noise before milking. Responses by animals would be expected to vary with noise type, level, time, and frequency.
The sound threshold expected to cause a behavioral response by animals is 85 to 95 decibels (dB). Changes in some blood composition parameters were described with 97 dB. General noise at 105 dB reduce milk yield, rate of milk release, and feed intake by dairy cows.
In a Swiss survey, noise and vibration together were studied on 50 dairy farms during milking to investigate effects on somatic cell count (SCC). The analysis indicated that SCC values increased with increasing vibrations, whereas noise did not affect SCC. Apparently, noise levels in this survey were lower compared to the threshold indicated previously. No correlation between vibration and noise was observed.
In the same Swiss study, 12 milking parlors (9 herringbone, 2 autotandem, and 1 side-by-side) were modified to reduce vibrations. Modifications included: (1) putting the vacuum pump on rubber supports, (2) using rubber tubing to connect the vacuum pump to the exhaust and the main conduit, (3) installing regulatory buffer tanks between the pumps and the conduits, (4) installing buffer tanks between the main conduit and the pulsator, (5) using absorbing ducts to install all tubes and tanks, and (6) connecting the pulsators with elastic and dampening tubes.
As a result, the SCC dropped on all 12 farms that had modified their milking systems to reduce vibrations.
Leakage of current from electrically powered machines can lead to undesirable electrical phenomenon called stray voltage, which is defined as a small voltage (<10V) measure between two points that can be simultaneously contacted by an animal. For several years, stray voltage was considered a possible factor impairing production.
A recent meta-analysis of stray voltage on dairy cattle combining results from 22 independent studies was published. The study indicated that production was not affected by exposure to contact current at levels of 3 mA or lower for exposures of up to 21 days or 4 weeks. The authors of this meta-analysis also concluded that the overall weighted mean for first behavioral response to current was 4.0 amperes (mA). This is in agreement with other studies where no overall decreases in feed and water consumption or milk production occurred below 4 V across an animal body or a body current of 4.0 mA.
Losses rise with current flow
In conclusion, the possibility of animal production losses increase when the amount of current that can flow through the animal body is more than 4 mA (60 Hertz (Hz).
A high speed train is being proposed to cross the Central Valley of California and the heart of the agricultural area in Merced County. A high speed train is a source of noise, vibration, and electromagnetic fields (California High-Speed Train Final Program EIR/EIS, http://www.cahighspeedrail.ca.gov/). Apparently, no effects of noise and vibrations have been described and /or studied on dairy animals.
The World Health Organization and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) have published recommendations for an exposure limit value for low-frequency electromagnetic fields and microwaves to protect people against nerve stimulation and body heating, respectively.
To this respect, a recent Australian study has been published. The authors carefully analyzed the information published in several countries and measured electromagnetic field strengths of the Australian transportation systems. The magnetic field strength was measured at different points inside the moving train, trams, and hybrid cars.
The results seem to be compatible with the evidence of laboratory studies on the biological effects that are found in the literature; nonetheless, the results are lower than those levels recommended by the ICNIRP. Researchers also indicated that there is much speculation and still have not sufficiently investigated impact of existing transportation systems (tram, train, hybrid vehicle, and high- speed maglev lines) on the environment, specifically on biological tissue that is exposed over a long period.